The growth which the computer and electronics industries have experienced in the last three decades has dramatically increased the demand for conductive networks (for example, printed circuit boards (PCB's)). This has led to the use of more densely packed electrical modules and circuits, each requiring multiple interconnections to one another. This requirement to increase printed circuit (PC) board density to accommodate yet another generation of new high power integrated circuit (IC) chips, combined with the requirement to incorporate surface mount technology, continues to drive PC board density to new levels of sophistication. However, there is a practical limit to the density that can be achieved using conventional circuit board connectors.
There is a great need for high quality, low cost, densely packed interconnect cables and equally densely packed connector clusters for coupling the cables to the surface mounted terminals of PC boards and modules. In a typical present day application, a floppy disk drive may require a flexible connection to a recording head whose conductors are only on the order of 0.2 mm (0.008 inches) on center. This means that the jumper's conductors must have a similar spacing. Also, the new liquid crystal displays have conductors which are even more closely packed, for example, 0.1 mm (0.004 inches) on center, and which must be interconnected to other PC boards and modules. Still further, there is growing use of ceramic PC boards to accommodate multiple IC chip arrays which also require high density connectors and customer interconnect cables for purposes of terminating those components.
As a direct result of the growth in the circuit board industry, there has been a parallel increase in the volume of environmentally-hazardous chemicals generated by the conventional etching and deposition processes. For example, it is not uncommon for one circuit board fabrication facility to generate 4000 liters (1,000 US gallons) per day of photoresist stripper and (4800 liters) (1,200 U.S. gallons) per week of developer solution. These toxic wastes must be transported off-site for proper disposal at hazardous waste management sites. Thus, there is an urgent need for a non-chemical method for the manufacture of conductive networks.
It is an object of this invention to provide relatively inexpensive, high-quality, densely packed, conductive network, contact clusters and connector assemblies with densely packed contact clusters having the self-aligning capabilities for use in fabricating rigid or flexible circuit boards, that can be built without the use or generation of environmentally hazardous chemicals.
A further object of the invention is to provide a connector assembly having contact clusters attached which significantly increase the number of signals that each contact position can interconnect and which are specially profiled to align and to interlock with the conductive paths of networks to which they are connected.
Yet another object of the invention is to provide methods of making conductive networks, contact clusters and connector assemblies having one or more of the above advantages.